validate sync IO in generateMetadata according to Page's prefetchable status by gnoff · Pull Request #90164 · vercel/next.js

gnoff · 2026-02-18T22:18:40Z

While metadata is generated using functions defined in many Segments the actual final resolved metadata belongs to the Page Segment specifically. This means that we need to treat the sync IO heuristic for metadata based on whether the Page is considered runtime prefetchable.

nextjs-bot · 2026-02-18T22:38:48Z

Stats from current PR

🔴 1 regression

Metric	Canary	PR	Change	Trend
node_modules Size	473 MB	473 MB	🔴 +61.7 kB (+0%)	▁▁▁▁▁

📊 All Metrics

📖 Metrics Glossary

Dev Server Metrics:

Listen = TCP port starts accepting connections
First Request = HTTP server returns successful response
Cold = Fresh build (no cache)
Warm = With cached build artifacts

Build Metrics:

Fresh = Clean build (no .next directory)
Cached = With existing .next directory

Change Thresholds:

Time: Changes < 50ms AND < 10%, OR < 2% are insignificant
Size: Changes < 1KB AND < 1% are insignificant
All other changes are flagged to catch regressions

⚡ Dev Server

Metric	Canary	PR	Change	Trend
Cold (Listen)	914ms	913ms	✓	▁▁▁▁▁
Cold (Ready in log)	896ms	897ms	✓	▁▁▁▁▁
Cold (First Request)	1.680s	1.701s	✓	▁▃▃▃▁
Warm (Listen)	913ms	914ms	✓	▁▁▁▁▁
Warm (Ready in log)	898ms	896ms	✓	▁▁▁▁▁
Warm (First Request)	698ms	678ms	✓	▂▂▂▁▁

📦 Dev Server (Webpack) (Legacy)

📦 Dev Server (Webpack)

Metric	Canary	PR	Change	Trend
Cold (Listen)	506ms	507ms	✓	▁▄▁█▁
Cold (Ready in log)	482ms	482ms	✓	▁▄▁█▃
Cold (First Request)	2.137s	2.138s	✓	▁▂▁█▂
Warm (Listen)	506ms	506ms	✓	▁▄▁█▁
Warm (Ready in log)	484ms	483ms	✓	▁▃▁█▃
Warm (First Request)	2.176s	2.132s	✓	▁▂▁█▂

⚡ Production Builds

Metric	Canary	PR	Change	Trend
Fresh Build	6.412s	6.354s	✓	▁▁▁▁▂
Cached Build	6.380s	6.413s	✓	▁▁▁▁▂

📦 Production Builds (Webpack) (Legacy)

📦 Production Builds (Webpack)

Metric	Canary	PR	Change	Trend
Fresh Build	15.815s	15.791s	✓	▁▂▁█▁
Cached Build	15.929s	15.959s	✓	▁▂▁█▁
node_modules Size	473 MB	473 MB	🔴 +61.7 kB (+0%)	▁▁▁▁▁

📦 Bundle Sizes

Bundle Sizes

⚡ Turbopack

Client

Main Bundles: **398 kB** → **398 kB** ⚠️ +5 B

80 files with content-based hashes (individual files not comparable between builds)

Server

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	758 B	769 B	🔴 +11 B (+1%)
Total	758 B	769 B	⚠️ +11 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	452 B	451 B	✓
Total	452 B	451 B	✅ -1 B

📦 Webpack

Client

Main Bundles

	Canary	PR	Change
5528-HASH.js gzip	5.47 kB	N/A	-
6280-HASH.js gzip	57 kB	N/A	-
6335.HASH.js gzip	169 B	N/A	-
912-HASH.js gzip	4.53 kB	N/A	-
e8aec2e4-HASH.js gzip	62.6 kB	N/A	-
framework-HASH.js gzip	59.7 kB	59.7 kB	✓
main-app-HASH.js gzip	256 B	254 B	✓
main-HASH.js gzip	39.1 kB	39.1 kB	✓
webpack-HASH.js gzip	1.68 kB	1.68 kB	✓
262-HASH.js gzip	N/A	4.53 kB	-
2889.HASH.js gzip	N/A	169 B	-
5602-HASH.js gzip	N/A	5.48 kB	-
6948ada0-HASH.js gzip	N/A	62.6 kB	-
9544-HASH.js gzip	N/A	57.8 kB	-
Total	231 kB	231 kB	⚠️ +726 B

Polyfills

	Canary	PR	Change
polyfills-HASH.js gzip	39.4 kB	39.4 kB	✓
Total	39.4 kB	39.4 kB	✓

Pages

	Canary	PR	Change
_app-HASH.js gzip	194 B	194 B	✓
_error-HASH.js gzip	183 B	180 B	🟢 3 B (-2%)
css-HASH.js gzip	331 B	330 B	✓
dynamic-HASH.js gzip	1.81 kB	1.81 kB	✓
edge-ssr-HASH.js gzip	256 B	256 B	✓
head-HASH.js gzip	351 B	352 B	✓
hooks-HASH.js gzip	384 B	383 B	✓
image-HASH.js gzip	580 B	581 B	✓
index-HASH.js gzip	260 B	260 B	✓
link-HASH.js gzip	2.5 kB	2.5 kB	✓
routerDirect..HASH.js gzip	320 B	319 B	✓
script-HASH.js gzip	386 B	386 B	✓
withRouter-HASH.js gzip	315 B	315 B	✓
1afbb74e6ecf..834.css gzip	106 B	106 B	✓
Total	7.97 kB	7.97 kB	✅ -2 B

Server

Edge SSR

	Canary	PR	Change
edge-ssr.js gzip	125 kB	125 kB	✓
page.js gzip	251 kB	252 kB	✓
Total	376 kB	376 kB	⚠️ +262 B

Middleware

	Canary	PR	Change
middleware-b..fest.js gzip	616 B	612 B	✓
middleware-r..fest.js gzip	156 B	155 B	✓
middleware.js gzip	43.8 kB	43.6 kB	✓
edge-runtime..pack.js gzip	842 B	842 B	✓
Total	45.4 kB	45.2 kB	✅ -160 B

Build Details

Build Manifests

	Canary	PR	Change
_buildManifest.js gzip	715 B	718 B	✓
Total	715 B	718 B	⚠️ +3 B

Build Cache

	Canary	PR	Change
0.pack gzip	3.91 MB	3.92 MB	🔴 +15 kB (+0%)
index.pack gzip	105 kB	104 kB	✓
index.pack.old gzip	104 kB	105 kB	✓
Total	4.12 MB	4.13 MB	⚠️ +14.9 kB

🔄 Shared (bundler-independent)

Runtimes

	Canary	PR	Change
app-page-exp...dev.js gzip	316 kB	317 kB	✓
app-page-exp..prod.js gzip	168 kB	168 kB	✓
app-page-tur...dev.js gzip	316 kB	316 kB	✓
app-page-tur..prod.js gzip	168 kB	168 kB	✓
app-page-tur...dev.js gzip	313 kB	313 kB	✓
app-page-tur..prod.js gzip	166 kB	166 kB	✓
app-page.run...dev.js gzip	313 kB	313 kB	✓
app-page.run..prod.js gzip	166 kB	166 kB	✓
app-route-ex...dev.js gzip	70.6 kB	70.6 kB	✓
app-route-ex..prod.js gzip	49.1 kB	49.1 kB	✓
app-route-tu...dev.js gzip	70.6 kB	70.6 kB	✓
app-route-tu..prod.js gzip	49.1 kB	49.1 kB	✓
app-route-tu...dev.js gzip	70.2 kB	70.2 kB	✓
app-route-tu..prod.js gzip	48.9 kB	48.9 kB	✓
app-route.ru...dev.js gzip	70.2 kB	70.2 kB	✓
app-route.ru..prod.js gzip	48.9 kB	48.9 kB	✓
dist_client_...dev.js gzip	324 B	324 B	✓
dist_client_...dev.js gzip	326 B	326 B	✓
dist_client_...dev.js gzip	318 B	318 B	✓
dist_client_...dev.js gzip	317 B	317 B	✓
pages-api-tu...dev.js gzip	43.2 kB	43.2 kB	✓
pages-api-tu..prod.js gzip	32.9 kB	32.9 kB	✓
pages-api.ru...dev.js gzip	43.2 kB	43.2 kB	✓
pages-api.ru..prod.js gzip	32.8 kB	32.8 kB	✓
pages-turbo....dev.js gzip	52.5 kB	52.5 kB	✓
pages-turbo...prod.js gzip	38.4 kB	38.4 kB	✓
pages.runtim...dev.js gzip	52.5 kB	52.5 kB	✓
pages.runtim..prod.js gzip	38.4 kB	38.4 kB	✓
server.runti..prod.js gzip	63.6 kB	63.6 kB	✓
Total	2.8 MB	2.8 MB	⚠️ +549 B

📝 Changed Files (10 files)

Files with changes:

app-page-exp..ntime.dev.js
app-page-exp..time.prod.js
app-page-tur..ntime.dev.js
app-page-tur..time.prod.js
app-page-tur..ntime.dev.js
app-page-tur..time.prod.js
app-page.runtime.dev.js
app-page.runtime.prod.js
pages-api.runtime.dev.js
pages.runtime.dev.js

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app-page-tur..ntime.dev.js

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app-page-tur..ntime.dev.js

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app-page-tur..time.prod.js

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app-page.runtime.prod.js

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pages.runtime.dev.js

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… status While metadata is generated using functions defined in many Segments the actual final resolved metadata belongs to the Page Segment specifically. This means that we need to treat the sync IO heuristic for metadata based on whether the Page is considered runtime prefetchable.

nextjs-bot added created-by: Next.js team PRs by the Next.js team. tests type: next labels Feb 18, 2026

gnoff requested a review from lubieowoce February 18, 2026 22:19

Base automatically changed from jstory/sync-io-runtime-boundary to canary February 18, 2026 22:49

gnoff added 2 commits February 18, 2026 14:50

8c360e4

gnoff force-pushed the jstory/sync-io-prefetch-metadata branch from d0f6ebe to 8c360e4 Compare February 18, 2026 22:50

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validate sync IO in generateMetadata according to Page's prefetchable status#90164

validate sync IO in generateMetadata according to Page's prefetchable status#90164
gnoff wants to merge 2 commits intocanaryfrom
jstory/sync-io-prefetch-metadata

gnoff commented Feb 18, 2026

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nextjs-bot commented Feb 18, 2026 •

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gnoff commented Feb 18, 2026

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nextjs-bot commented Feb 18, 2026 •

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